WIRING SUBSTRATE AND PRODUCTION METHOD THEREFOR

A wiring substrate includes an insulation substrate, a through hole, an upper-surface-side land conductor, a lower-surface-side land conductor, and a through hole conductor. The insulation substrate includes a first insulation layer, a second insulation layer, and a glass fiber layer provided between the first and second insulation layers. The through hole has a diameter which decreases from the upper surface of the insulation substrate toward the interior thereof, which becomes smallest at the glass fiber layer, and which increases from the glass fiber layer toward the lower surface of the insulation substrate. The upper-surface-side land conductor and the lower-surface-side land conductor respectively cover the upper-surface-side and lower-surface-side openings of the through hole. The through hole conductor is formed in the through hole. The upper-surface-side opening of the through hole has a diameter larger than that of the lower-surface-side opening of the through hole, and the upper-surface-side land conductor has a diameter larger than that of the lower-surface-side land conductor.